Spot detector



Jan. 26, 1954 R. WALZ 2,667,552

SPOT DETECTOR Filed July 26, 1950 If i i- 25-7 24 I 17 1,; I I I 5 i Him 3 19 I INVENTOR.

fade/14k [Va/[Z E Mu M KM fl TTOPIVEYS Patented Jan. 26, 1954 1" OFFICE SPOT DETECTOR Rudolph Walz, Fayson Lakes, N. J., assignor to J. H. Scharff, Inc., Orange, N. J., a corporation of New Jersey Application July 26, 1950, Serial No. 175,916

6 Claims.

This invention relates to a structurally and functionally improved detecting apparatus, fi pecially useful in operating alarm or registering apparatus when excessive heat. conditions dangerous to property arise; the present invention thus lending itself ideally to. the initiation of an alarm under such circumstances. However, apparatus constructed in accordance with the present teachings may also be employed for purposes other than merely registering or sounding an alarm.

It" is an object ofthe invention to furnish a unit. of this type. which may be conveniently mounted or installed in desired locations of di verse character and. which will operate efficiently where a pre-determined fixed temperature. is exceeded or where a rise of temperature has occurred in less than a certain minimum period of time.

Moreover, in accordance with the present teachings the' apparatusv will be self-restoring and will not be afiected by dust or other foreign materials.

An additional object is'that of, furnishing a device of this type which will include relatively few parts, each individually simple and rugged in construction and operating over long periods of time with freedom from all difliculties.

With these and other objects in mind reference is bad to the attached sheet of drawings illustrating one practicalembodiment of the invention and in which:

Fig. 1 is a sectional side view ofthe detector taken along the line I- and in the direction of the arrows as indicated in Fig. 2:

Fig. 2 is a bottom plan view of the device with certain of the encasing portions removed and with others broken away to disclose inner structures;

Fig. 3 is a. transverse sectional view taken along the' line 3..3 and in the direction of the arrows ably includes a central portion 1 formed with an 1 opening a and additionally mbraces various sure faces contoured-to provide mountings for the parts as hereinafter described. The base may terminate in a downwardly extending flange 9 provided with one or more lead-accommodating openings Ill. The latter may be initially closed by knockouts and which are removed when necessary for the convenient passage of leads connected to the unit.

A cover preferably in the form of a dome H is provided. This unit is formed of a metal having high thermal conductivity. Preferably there extends across the dome an integral ribportion [2. Such rib portion serves to strengthen the dome and make it resistant to flexing or distortion. Disposed within the groove thus formed in the inner face of the dome is a bimetallic strip [3. The latter may be secured by rivets or soldering at a point adjacent that at which the dome is supported on the base. The upper end of strip I3 is free and preferably carries an insulating disl: It. A shoulder may define the outermost or central portion 1 of the base. This shoulder has a diameter equal to that of the dome l2. As shown, these parts are overlapped and a press fit exists between them. Prior to mounting the cooperat ng. surfaces may be coated with a film of cement. In this manner the parts are retained against displacement and an air tight fit is assured.

Disposed within dome l2 and upon the outermost portion of the base is a strip l5. The latter is convenientlyformed of bronze. One of its ends is preferably secured against displacement with respect to the base by, for example, a terminal in Its central portion is the form of a bolt is. bowed upwardly in line with the insulating disk l4. Its opposite end is extended downwardly and outwardly. That end may terminate in a laterally extending portion I1 spaced from the outer face of the base. Carried by the base and under lying this end of stri I 5 is a contact which may embrace a set screw 18. From the latter a strip Ill extends in electrical engagement with a terminal 28. Similarly a conducting strip 21 may extend from bolt I6 through to terminal 22.

Leads (not shown) are connected to terminals 20 and 22. These leads, in accordance with conventional construction, are coupled to a source of electric current supply and to the registering or other mechanism which is to be actuated when conditions of dan er exist.

Disposed inwardly of the central portion! or the base is a di phragm 2a The latter is prefers ably formed of corrosion-resistant metal and conveniently provided with concentric corrugations. Whileit will be highly sensitive to pressures of low value, it will also be relatively strong and resistant to shocks and other abuses. As shown, it may centrally mount a contact 24 of suitable metal. Its side edges are conveniently flared outwardly to provide a flange portion 25. The latter bears against the inner face of the central portion 1 of the base and is maintained in this position by a mounting ring 26 of dielectric material. To assure an air tight fit a film of cement may be applied to the flange 25 prior to the mounting of the diaphragm. Therefore, when ring 26 is brought into firm contact with flange 25 and the latter is in turn caused to intimately engage the inner face of base portion I, a seal is provided which will remain effective for long periods of time even when subjected to high temperatures.

Underlying diaphragm 23 and bearing against the lower edge of ring 26 is a bridge portion 21. The latter may conveniently be formed of bronze. It adjustably mounts a contact screw 28. As shown, especially in Figs. 1 and 2, strip is is continued beyond the assembly indicated at is and is secured in electrical connection with screw 28. That screw extends in line with contact 24. A cover 29 is applied to the inner surface of the base and closes the lower portion of the assembly. This cover will have a relatively snug fit with respect to adjacent surfaces. However it is provided with openings or notches through which strips l9 and 2| extend. By virtue of these and/or other openings passages are provided such that an adequate air flow may occur into and from the space directly enclosed by the cover.

A breather valve or passage is furnished by conveniently utilizing a tube 30. The latter has its upper end extending in communication with the space defined by dome l2. The body of this tube may extend below the central portion 1 of the base to a point adjacent the inner face of cover 29. Tube 30 is constricted as at 3| to furnish a substantially reduced passage. Thus, in effect, a metering structure is provided which will allow of a seepage of air into and from the base enclosed by the dome. Obviously, other forms of breather. tube or valve structures might be employed in lieu of that herein illustrated. As is apparent and under all circumstances the parts are so proportioned or calibrated that a flow corresponding to that suitable for the needs of a given installation is provided for. The centralportion I of the base is formed with a further passage which is continued in the bore of a plug 3| extending into the space defined by cover 29. This bore permits of a setting of the parts, as hereinafter described. After the setting has once been effected then the plug bore may be sealed by a. block or stopper 32.

The parts are assembled to provide a unit as shown in the drawings. will maintain diaphragm 23 in mounted position and sealed as aforedescribed. As the securing bolts or screws mounting bridge member 21 are tightened that member will bear against the lower edge of ring 26 to maintain it against any probability of displacement. Thus, danger of 'air leakage is prevented. Contact screw 28 is adjusted to be spaced a proper distance from contact 24. This result is achieved by connecting plug 3| with a source of air under predetermined pressure and to create a similar pressure within dome I 2. Screw 28 is, under, these circumstances, brought into engagement with contact 24. That screw is now locked conven- So assembled ring 26 engage set screw '28.

4 iently by a nut and locking ring assembly. With the source of air under pressure disconnected from plug 3| the bore of the latter may be sealed by the block or stopper 32. In an abundance of caution a cement fllm may be applied to the locking assembly for screw 28 as well as to the block or stopper 32 and the parts of the set screw assembly l8. Other parts may likewise be coated if desired. As afore brought out the breather tube or valve 30 provides a passage of reduced cross section having an area proper for the needs of a given installation. This installationcontrary to systems as heretofore provideduses no medium for the air flow. Accordingly changes in the rate of air flow caused by atmospheric conditions or conditions existing in plants is, in efiect, eliminated. Spring strip [5 is so applied to the base and maintained against movement with respect to the same that it cannot change its horizontal position adjacent bolt l 6. Insulating disk l4 or its equivalent prevents electrical connection being established between this strip and the dome l2 or other undesired parts. The laterally extending end portion I! of strip l5 may be conveniently silver plated or otherwise treated to assure of a ready flow of current. The same is trueof contacts 24 and screws I8 and 28. Due to the fact that strip I3 is in direct engagement with the dome l2, heat will be immediately transferred from the latter to the bimetallic strip when heat is generated exteriorly of the unit. Any excess of wire connected to terminals 28 and 22 may be housed within the space existent between cover 29 and the outer edge of flange 9.

Under normal conditions of temperature variation the air confined within dome I2 is maintained at atmospheric pressure. This will be because of the valve 30 which permits air to slowly enter or escape from this space according to then existing conditions. However, any sudden change of temperature as caused by an abnormal heat condition in an area or compartment protected by one or more of the detectors will expand the air within dome I2. This will create a pressure on the inner face of diaphragm 23 because the pressure will be transmitted through opening 8. Asa result contact 24 will Thus, the circuit is closed and an alarm is given and/or desired apparatus is actuated. As will be apparent, the creation of an adequate pressure to achieve this result will occur because the opening afforded by valve or tube 30 is so small that the air expanded by the heat cannot escape fast enough to prevent an engagement between contact 24 and set screw 28. As will also be apparent this rate of rise system or structure can be adapted to normal I as well as abnormal temperature conditions simbear against the central portion of spring I! and force the end of the same into contact with the assembly, l8. Thus, an alarm will be given as soon as the temperature has reached a certain pre-determlned point. By using bimetals with different characteristics and by properly adjust ing the parts, the fixed temperature characteristic of the unit can be depended upon to operate under ordinary as well as under extraordinary high and intermediate heat conditions as they arise in any given installation.

After the condition causing the high tempera.- ture has been corrected and the temperature drops below the operating point of the detector, the bimetallic strip l3 will return to its original position. Accordingly the apparatus will be reset for a subsequent operation. The same is true in considering the rapid rate of ris structure or system characteristics of the unit. As will be apparent due to the provision of the breather valve 36, the diaphragm and other self-restoring parts will return to a normal position after the dangerous condition has ceased to exist.

As will be understood due to the fact that the breather tube 36 uses no medium for the air flow, the dangers of clogging of that tube, with consequent faulty operation of the device are avoided. Under certain conditions plug 3i may be eliminated and merely the opening through which the breather tube 3i! passes used for testing purposes. The configuration of strip 55 may be varied in numerous respects. Also if desired and contrary to the showing in the drawings the position of the dome i2 might be shifted through 180. Under these circumstances, the bimetallic strip l3 would extend above and adjacent the bolt It. With such an arrangement of parts the movements of the spring strip it will be achieved in a more desirable manner.

Thus a spot detector or unit is provided which will furnish a structure to dependably respond to a rapid rate of rise, as well as the exceeding of a pre-determined temperatures. It is apparent that among others the several objects of the invention as specifically aforenoted are achieved. Obviously numerous changes in construction and rearrangement of the parts might be resorted to without departing from the spirit of the invention as defined by the claims.

Iclaim:

l. A detector including in combination a base of insulating material, shell of heat conducting material secured to said base, a bimetallic strip having one end secured against movement with respect to said shell and its body extending adjacent the inner face of the latter and terminating in a free end at a point intermediate the edges of said shell, aspring strip disposed within said shell, means for securing one end of said spring strip against movement with respect to said base, a contact carried by said base and engageable by the opposite spring strip end and said bimetallic strip engaging the body of said spring strip with its free end at a point between the ends of said spring strip to rock the latter around the end secured to said base and cause said opposite strip end to have amplified movement towards and out of engagement with said contact.

2. A detector including in combination a base of insulating material, a shell of heat conducting material secured to said base, a bimetallic strip having one end secured against movement with respect to said shell and its body extending adjacent the inner face of the latter and terminating in a free end at a point intermediate the edges of said shell, a spring strip disposed within said shell, means for securing one end of said spring strip against movement with respect to said base, a contact carried by said base and engageable by the opposite spring strip end, said bimetallic strip engaging th body of said spring strip with its free end at a point between the ends of said spring strip to rock the latter around the end secured to said base and cause said opposite strip end to have amplified movement towards and out of engagement with said contact, said shell being formed with a groove in its inner face, said groove reenforcing said shell and said bimetallic strip in one of its extreme positions, having substantially its entire body disposed within said roove in contact with the adjacent shell face.

3. A detector including in combination a base of insulating material, a shell of heat conducting material secured to said base, a diaphragm also secured to said base and providing in cooperation with said shell an air pressure chamber, a contact supported by said base and adapted to be placed in electrical connection with said diaphragm as the latter flexes in response to increase in air pressure within said chamber, means providing a breather structure to permit of controlled flow of air into and from said chamber, a bimetallic strip having one end secured against movement with respect to said shell and its body extending adjacent the'inner face of the latter and terminating in a free end at a point intermediate the edges of said shell, a spring strip disposed between said shell and diaphragm with its ends extending into the space intervening said shell and diaphragm, means for securing one end of said spring strip against movement with respect to said base, a contact can ried by said base and engageable by the opposite strip end, the free end of said bimetallic strip engaging the body of said spring strip at a point between the ends of the, latter to rock said spring strip around its secured end and cause said opposite strip end to have amplified movement toward and out of engagement with. said contact and a centrally apertured portion forming a part of said base and intervening said spring strip and diaphragm.

l. A. detector including in combination a base of insulating material, a shell of heat conducting material secured to said base, a diaphragm also secured to said base and providing in cooperation with said shell an air pressure chamber, a contact supported by said base and adapted to be placed in electrical connection with said diaphragm as the latter flexes in response to increase in air pressure within said chamber, means providing a breather structure to permit of a controlled fiow of air into and from said chamber, a bimetallic strip having one end secured against movement with respect to said shell and its body extending adjacent the inner face of the latter and terminating in a free end at a point intermediate the edges of said shell, a spring strip disposed between said shell and diaphragm with its ends extending into the space intervening said shell and diaphragm, means for securing one end of said spring strip against movement with respect to said base, a contact carried by said base and engageable by the opposite strip end, the free end of said bimetallic strip engaging the body of said spring strip at a point between the ends of the latter to rock said spring strip around its secured end and cause said opposite strip end to have amplified movement towards and out of engagement with said contact, a centrally apertured portion forming apart of said base and the latter being recessed in line with portion adjacent the surface of the central base portion and a mounting ring bearing against said flange and the adjacent base surfaces to maintain said diaphragm in substantially air-tight engagement with said base. 7

5. A detector including in combination a base of insulating material, a shell of heat conducting material secured to said base, a diaphragm also secured to said base and providing in cooperation with said shell an air pressure chamber, a contact supported by said base and adapted to be placed in electrical connection with said diaphragm as the latter flexes in response to increase in air pressure within said chamber, means providing a breather structure to permit of a controlled flow of air into and from said chamber, a bimetallic strip having one end secured against movement with respect to said shell and its body extending adjacent the inner face of the latter and terminating in a free end at a point intermediate the edges of said shell, a spring strip disposed between said shell and diaphragm with its ends extending into the space intervening said shell and diaphragm, means for securing one end of said spring strip against movement with respect to said base, a contact carried by said base and engageable by the opposite strip end, the free end of said bimetallic strip engaging the body of said spring strip at a point between the ends of the latter to rock said spring strip around its secured end and cause said opposite strip end to have amplified movement towards and out of engagement with said contact, a centrally apertured portion forming a part of said base and the latter being recessed in line with said portion, an outwardly extending flange at the edge of said diaphragm, said diaphragm being disposed within said recess and with its flange portion adjacent the surface of the central base portion, a mounting ring bearing against said flange and the adjacent base surfaces to maintain said diaphragm in substantially air-tight engagement with said base and a bridge portion secured to said base and bearing against said ring to prevent a displacement of the latter.

6. A detector including in combination a base of insulating material, a shell of heat conducting material secured to said base, a diaphragm also secured to said base and providing in cooperation with said shell an air pressure chamber, a contact supported by said base and adapted to be placed in electrical connection with said diaphragm as the latter flexes in response to increase in air pressure within said chamber, means providing a breather structure to permit of a controlled flow of air into and from said chamber, a bimetallic strip having one end secured against movement with respect to said shell and its body extending adjacent the inner face of the latter and terminatingin a free end at a point intermediate the edges of said shell, a spring strip disposed between said shell and diaphragm with its ends extending into the space intervening said shell and diaphragm, means for securing one end of said spring strip against movement with respect to said base, a contact carried by said base and engageable by the opposite strip end, the free end of said bimetallic strip engaging the body of said spring strip at a point between the ends of the latter to rock said spring strip around its secured end and cause said opposite strip end to have amplified movement towards and out of engagement with said contact, a centrally apertured portion forming a part of said base and intervening said spring strip and diaphragm and a cover secured to said base and enclosing the outer surface of said diaphragm.

RUDOLPH WALZ.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 989,347 Goldstein Apr. 11, 1911 1,018,253 McWilliams et al. Feb. 20, 1912 1,176,460 Kayser et a1 Mar. 21, 1916 1,723,965 Behringer Aug. 6, 1929 2,158,850 Campbell May 16, 1939 2,191,670 Kuhn et al. Feb. 27, 1940 2,209,193 Derby July 23, 1940 2,267,484 Van Houten Dec. 23, 1941 2,286,459 Braun June 16, 1942 2,428,838 Derby Oct. 14, 1947 

